Expansible nut unable to work loose



March 1937- M. BOURDON DE-LAUNAY 2,074,779

EXPANSIBLE NUT UNABLE TO WORK LOOSE Filed July 6, 1934 Fig.1 1592 m. gomcm 04 az Patented Mar. 23, 1937 EXPANSIBLE NUT Maurice Bourdon de Launay, Le Quillio, France UNABLE TO WORK Application July 6, 1934, Serial No. 734,036 In France July 10, 1938 1 Claim.

This invention relates to an expansible nut unable to'work loose, constituted by a wire wound on itself about a mandrel having the desired diameter, so that the turns, which must be in con- 5 tact with each other, form a kind of tube, the

hollow central element obtained being-.subsequently internally screw-threaded according to the desired pitch.

Thewire used can have any suitable cross section; however, in order to obtain turns which fimrlyfit against each other, as well at themterior as at the interior, use will preferably be made of a wire having a trapezoidal cross section; this wire, after it has been wound edgewise on the: mandrel assumes a rectangular or approximately rectangular cross section.

Fig. 1 is a cross section of the wire before winding.

so as to present a plurality of sides; tapping is then effected, preferably by means of a semiconical tap having a long stenr, so that it is not necessary to move the tap backwardsfor removing it from the nut, this tapping being eficte d 'l" in the direction in which the turns are wound.

It will be understood that if such a nut is screwed'omcrew threadedlod having a diameter slightly greater to the extent of a few tenths of a millimeter than the tap which has been used 10 for W internally threading the nut, the screwthreaded rod can enter the nut only by expanding it to the extent of the few tenths of a millimeter it has in excess, and if it is then attempted to unscrew it as an ordinary nut, this-operation 15 will be impossible, as it would have for effect to tighten its turns so much more powerfully as the stress exerted will be greater; it will be possible Figr 2-is-acrosssection'of-the'wireafterbeing mwthemwenly byacting on the turn wound into a nut.

Fig. 3 is a vertical cross section of a nut made according to the present invention and externally shaped.

Fig. 4 shows this nut after it has been internally screw-threaded."

Fig. 5 is plarrview of the nut. Figs 6' and '7 illustrate the adjunction to this "iii of members preventing it from being removed. Thus, the nut forming the subjectmatter of the present invention, instead of being machined in the lathe as ordinary nuts, is constituted by a wire, of suitable cross section as indicated above, wound edgewise about a mandrel having a diameter equal to that of the hole which should have been bored'in the metal barrier forming an ordinaryrnutnthe'outerrhameter of the nut will of course depend on the cross section of the wire used, the dimensions of which will cor- 40 respond to the size of the nut to be made; a kind of slightly flexible tube will thus be obtained,

having, so to speak, the appearance of a coil spring the turns of which tightly fit against each other. i

5 In order to impart greater resiliency to the middle portion of the member thus obtained, the

width of the middle turns will be slightly reduced by forming therein a circular-groove,..as indicated at I in Fig. 3. V

The portions 2 and 3 forming the head and the shoulder or flange of the nut will be either milled,

or cut so as to have six or eight sides, as an ordinary nut, or cut so as to have two parallel sides,

. or provided ith two blind holes on the upper face the'base being, in this case, preferably out or turns 3 forming the base of th eiut byiorcing 20 the turns apart, from place to place on the screwthreaded rod, thus allowing the release of said nut.

For screwingon thisrimprovedenut thegsame method of procedure as for an ordinary nut is' adopted; however, it is preferable to act on the head 2 only, this rendering the screwing on operation easier; on the contrary, for unscrewing f the nut, it is absolutely necessary to actontlie base 3, asindicated-above; if the'middle turn or 30 turns were acted upon, it would be impossible to cause the nut to rotate in either direction; it is.f0r this reason that it is necessary to provide the groove I in the middle portion of the nut, a s well ior imparting greater resiliency to the: 35 turns of this middle portion, as above stated, as for preventing the wrench from acting on these turns when tightening or loosening the nut; it is to be pointed out that this nut has simply to be screwed home without having to lock it, the lock- 40 ing operation would only tend to distort the turns, which would diminish its adherence to the rod; the necessity of not locking this nut has led to give it an. external appearance distinctly different from ordinary nuts so that it should notbe 4 manipulated as the latter, particularly owing to the presence of .the groove I.

This nut should be tightened on a smooth washer and not on a Grover washer; for pre-- venting calking, a washer made of parchment, or 50 of any other relatively thin fibrous material, can' be arranged between the washer and the member to be clamped; when the improved nut is used as a lock-nut, it is also convenient to interpose a smooth washer between both nuts.

It will then be necessary, in thi c f?"enceishowge suflicient for preventing the turns'- screwing the nut, to act on the lower turn of the from remaining 111 eentaet' When the threads of r/ millimetfi of their end and would present at &advantage of creating at the top of the threads er adherence of the flanks of the threads of the rod and of the nut.

Instead of tapping the nut according to a diameter a few tenths of a millimeter smaller. greater accuracy would be obtained by internally 5 threading it to the exact diameter, then by reducing the diameter after tapping by tightening ing the nut; if the nut was to support great tenthe turns on a smaller mandrel, or again by sile stresses tending to distort it by causing the holding the nut in expandedrondition during the turns to straddle the threads of the screw-threadjppi ngpperatiomandbfillowing it to return to ed rod, the nut might be provided with arr/outer a smaller diameter by its own resiliency.

jacket or with a pressed or'fiaiifidTv asher which The rod, by entering the nut, would restore would prevent this straddling of the turns. The the screw-threads to their normal position and adjunction of a washer pressed in the shape of a the screw-threads of the rod and of the nut cup-like member 4 (Fig. 6) about the base, or of wouldalso have a better contact than that they 15 iacket 5 (Fig. I) surrounding the nut and made could have when the nut has smthreadeh of soft metal or of steel, will prevent the removal to a smaller diameter.

of the said nut since it can be unscrewed only The body of the nut is capable of expanding by acting on its base and that for having access in both its dimensions, that is to say, in diamto this base it would be necessary to damage or eter and in length, and, consequently, of reactto break the washer or the jacket. ing by its resiliency, at right angles and parallel If in addition to the tensile stress to be supto its ax an this ul an s yported, the screw-threaded rod is to be subjected The first of these efiects has alone been used to a stress tending to unscrew it (as the pivot in internally threading a nut to a diameter a Pin of the right-hand .pedal of a bicycle which few tenths of a millimeter smaller than that 0L must have a left-hand screw-thread so as not the r whr d r the second ese efto constantly unscrew), it would be convenient fects can be y p oy by using in this case, to wind the turns of the nut in a e pitch of which is Slightly Smaller than direction reverse to the tapping, that is to so. that of the screw-threaded rod, this difiference from right to left, if the screw has a right-hand. be n m ll n h to be ne rly negligible, when thread. and from left to right, if it has a lefttwo or three threadsfthateis to say the thickness hand thread. of a turn) are considered, 's differ- For screwing and unscrewing, it will be necessary to use a flat wrench so as to act only on the head, or on the base of the .nut; use can also be made of a tubular wrench, one of the ends of 5 which will serve to act on the base for unscrewing,

and the other end, provided with an inner bearing portion, can only act on the head for screwthe nut must engage with those of the screw threaded rod.

The turns then react parallel to the axis of eupper-turn-ior unscrewing it, that is to say the reverse of the operation indicated above when the turns of the nut are wound in the same directi as th screw. the nut, and this action will be .added to that threads of the rod; i thi ca th t can be already obtained in the direction of the diamiirmly locked without any ris'i'fif aigfJrt' ij it eter. 7 e l as this might happen in the first case under Consequently, the flexibility, instantaneousness slderation, that is to say when it was necessary and energy of the clamping i n at ri n l to act on the head of the nut for unscrewing it. to the axis will a s be increased. w n t th For obtaining a perfect cont t of {m g fact that the turns being no longer exactly in hreads of the rod andnf the nut ith6 'i h *contactwvitlneachQer, no friction will prevent ning the risk that they are in contact only at their reaction their apices, the tapping can be effected with a For a rod screw-threaded to 8 millimeters, tap having full screw-threads instead of a tap Ditch 125 for instance, the nut Will be l p to having screw-threads reduced t t extent of 7,8 millimeters, pitch 120 to 122. one eighth as is usual, and the nut will be As these two reactions, one at right angles, bored according to a diameter. slightly greater"*the other parallel to the axis are suflicient to prethan that of the core of the screw-threaded Vent Separately-the nut from bosemng'they can rod; use might also be made of a special tap obviouslybeused either separately, or, preferably, 55 the flanks of the screw-threads of which would Simultaneously be parallel to-each-other on a few tenths of What I claim as my invention and. desire to secure as Letters Patent is:-

Expansible lock nut comprising a. helical metal wire of rectangular cross section with the .turns in contact with each other, a screw thread cut on the inner wall of slightly smaller diameter that the screw threaded rod upon which it has to be screwed an a circular groove cut on the outer cylindrical wall lea n ea (1 a base said nut upon axial application to the threa ed rod being expanded to prevent retrograde movement.

their end a square cross section, or a square cross section with the angles cut off, the end of the threads might also be rounded; these taps would have for advantage that they cannot engage between the turns of the nut during the tapping operation.

These various taps present also the further aTfr \o npty space for receiving the filings or other fOrelEQbOGlEiwhi h might prevent prop- MAURICE BOURDON m: LaUNAY. 

